[mirror_ubuntu-bionic-kernel.git] / scripts / recordmcount.h

/*
 * recordmcount.h
 *
 * This code was taken out of recordmcount.c written by
 * Copyright 2009 John F. Reiser <jreiser@BitWagon.com>.  All rights reserved.
 *
 * The original code had the same algorithms for both 32bit
 * and 64bit ELF files, but the code was duplicated to support
 * the difference in structures that were used. This
 * file creates a macro of everything that is different between
 * the 64 and 32 bit code, such that by including this header
 * twice we can create both sets of functions by including this
 * header once with RECORD_MCOUNT_64 undefined, and again with
 * it defined.
 *
 * This conversion to macros was done by:
 * Copyright 2010 Steven Rostedt <srostedt@redhat.com>, Red Hat Inc.
 *
 * Licensed under the GNU General Public License, version 2 (GPLv2).
 */
#undef append_func
#undef is_fake_mcount
#undef fn_is_fake_mcount
#undef MIPS_is_fake_mcount
#undef sift_rel_mcount
#undef find_secsym_ndx
#undef __has_rel_mcount
#undef has_rel_mcount
#undef tot_relsize
#undef do_func
#undef Elf_Addr
#undef Elf_Ehdr
#undef Elf_Shdr
#undef Elf_Rel
#undef Elf_Rela
#undef Elf_Sym
#undef ELF_R_SYM
#undef Elf_r_sym
#undef ELF_R_INFO
#undef Elf_r_info
#undef ELF_ST_BIND
#undef fn_ELF_R_SYM
#undef fn_ELF_R_INFO
#undef uint_t
#undef _w
#undef _align
#undef _size

#ifdef RECORD_MCOUNT_64
# define append_func		append64
# define sift_rel_mcount	sift64_rel_mcount
# define find_secsym_ndx	find64_secsym_ndx
# define __has_rel_mcount	__has64_rel_mcount
# define has_rel_mcount		has64_rel_mcount
# define tot_relsize		tot64_relsize
# define do_func		do64
# define is_fake_mcount		is_fake_mcount64
# define fn_is_fake_mcount	fn_is_fake_mcount64
# define MIPS_is_fake_mcount	MIPS64_is_fake_mcount
# define Elf_Addr		Elf64_Addr
# define Elf_Ehdr		Elf64_Ehdr
# define Elf_Shdr		Elf64_Shdr
# define Elf_Rel		Elf64_Rel
# define Elf_Rela		Elf64_Rela
# define Elf_Sym		Elf64_Sym
# define ELF_R_SYM		ELF64_R_SYM
# define Elf_r_sym		Elf64_r_sym
# define ELF_R_INFO		ELF64_R_INFO
# define Elf_r_info		Elf64_r_info
# define ELF_ST_BIND		ELF64_ST_BIND
# define fn_ELF_R_SYM		fn_ELF64_R_SYM
# define fn_ELF_R_INFO		fn_ELF64_R_INFO
# define uint_t			uint64_t
# define _w			w8
# define _align			7u
# define _size			8
#else
# define append_func		append32
# define sift_rel_mcount	sift32_rel_mcount
# define find_secsym_ndx	find32_secsym_ndx
# define __has_rel_mcount	__has32_rel_mcount
# define has_rel_mcount		has32_rel_mcount
# define tot_relsize		tot32_relsize
# define do_func		do32
# define is_fake_mcount		is_fake_mcount32
# define fn_is_fake_mcount	fn_is_fake_mcount32
# define MIPS_is_fake_mcount	MIPS32_is_fake_mcount
# define Elf_Addr		Elf32_Addr
# define Elf_Ehdr		Elf32_Ehdr
# define Elf_Shdr		Elf32_Shdr
# define Elf_Rel		Elf32_Rel
# define Elf_Rela		Elf32_Rela
# define Elf_Sym		Elf32_Sym
# define ELF_R_SYM		ELF32_R_SYM
# define Elf_r_sym		Elf32_r_sym
# define ELF_R_INFO		ELF32_R_INFO
# define Elf_r_info		Elf32_r_info
# define ELF_ST_BIND		ELF32_ST_BIND
# define fn_ELF_R_SYM		fn_ELF32_R_SYM
# define fn_ELF_R_INFO		fn_ELF32_R_INFO
# define uint_t			uint32_t
# define _w			w
# define _align			3u
# define _size			4
#endif

/* Functions and pointers that do_file() may override for specific e_machine. */
static int fn_is_fake_mcount(Elf_Rel const *rp)
{
	return 0;
}
static int (*is_fake_mcount)(Elf_Rel const *rp) = fn_is_fake_mcount;

static uint_t fn_ELF_R_SYM(Elf_Rel const *rp)
{
	return ELF_R_SYM(_w(rp->r_info));
}
static uint_t (*Elf_r_sym)(Elf_Rel const *rp) = fn_ELF_R_SYM;

static void fn_ELF_R_INFO(Elf_Rel *const rp, unsigned sym, unsigned type)
{
	rp->r_info = _w(ELF_R_INFO(sym, type));
}
static void (*Elf_r_info)(Elf_Rel *const rp, unsigned sym, unsigned type) = fn_ELF_R_INFO;

/*
 * MIPS mcount long call has 2 _mcount symbols, only the position of the 1st
 * _mcount symbol is needed for dynamic function tracer, with it, to disable
 * tracing(ftrace_make_nop), the instruction in the position is replaced with
 * the "b label" instruction, to enable tracing(ftrace_make_call), replace the
 * instruction back. So, here, we set the 2nd one as fake and filter it.
 *
 * c:	3c030000	lui	v1,0x0		<-->	b	label
 *		c: R_MIPS_HI16	_mcount
 *		c: R_MIPS_NONE	*ABS*
 *		c: R_MIPS_NONE	*ABS*
 * 10:	64630000	daddiu	v1,v1,0
 *		10: R_MIPS_LO16	_mcount
 *		10: R_MIPS_NONE	*ABS*
 *		10: R_MIPS_NONE	*ABS*
 * 14:	03e0082d	move	at,ra
 * 18:	0060f809	jalr	v1
 * label:
 */
#define MIPS_FAKEMCOUNT_OFFSET	4

static int MIPS_is_fake_mcount(Elf_Rel const *rp)
{
	static Elf_Addr old_r_offset;
	Elf_Addr current_r_offset = _w(rp->r_offset);
	int is_fake;

	is_fake = old_r_offset &&
		(current_r_offset - old_r_offset == MIPS_FAKEMCOUNT_OFFSET);
	old_r_offset = current_r_offset;

	return is_fake;
}

/* Append the new shstrtab, Elf_Shdr[], __mcount_loc and its relocations. */
static void append_func(Elf_Ehdr *const ehdr,
			Elf_Shdr *const shstr,
			uint_t const *const mloc0,
			uint_t const *const mlocp,
			Elf_Rel const *const mrel0,
			Elf_Rel const *const mrelp,
			unsigned int const rel_entsize,
			unsigned int const symsec_sh_link)
{
	/* Begin constructing output file */
	Elf_Shdr mcsec;
	char const *mc_name = (sizeof(Elf_Rela) == rel_entsize)
		? ".rela__mcount_loc"
		:  ".rel__mcount_loc";
	unsigned const old_shnum = w2(ehdr->e_shnum);
	uint_t const old_shoff = _w(ehdr->e_shoff);
	uint_t const old_shstr_sh_size   = _w(shstr->sh_size);
	uint_t const old_shstr_sh_offset = _w(shstr->sh_offset);
	uint_t t = 1 + strlen(mc_name) + _w(shstr->sh_size);
	uint_t new_e_shoff;

	shstr->sh_size = _w(t);
	shstr->sh_offset = _w(sb.st_size);
	t += sb.st_size;
	t += (_align & -t);  /* word-byte align */
	new_e_shoff = t;

	/* body for new shstrtab */
	ulseek(fd_map, sb.st_size, SEEK_SET);
	uwrite(fd_map, old_shstr_sh_offset + (void *)ehdr, old_shstr_sh_size);
	uwrite(fd_map, mc_name, 1 + strlen(mc_name));

	/* old(modified) Elf_Shdr table, word-byte aligned */
	ulseek(fd_map, t, SEEK_SET);
	t += sizeof(Elf_Shdr) * old_shnum;
	uwrite(fd_map, old_shoff + (void *)ehdr,
	       sizeof(Elf_Shdr) * old_shnum);

	/* new sections __mcount_loc and .rel__mcount_loc */
	t += 2*sizeof(mcsec);
	mcsec.sh_name = w((sizeof(Elf_Rela) == rel_entsize) + strlen(".rel")
		+ old_shstr_sh_size);
	mcsec.sh_type = w(SHT_PROGBITS);
	mcsec.sh_flags = _w(SHF_ALLOC);
	mcsec.sh_addr = 0;
	mcsec.sh_offset = _w(t);
	mcsec.sh_size = _w((void *)mlocp - (void *)mloc0);
	mcsec.sh_link = 0;
	mcsec.sh_info = 0;
	mcsec.sh_addralign = _w(_size);
	mcsec.sh_entsize = _w(_size);
	uwrite(fd_map, &mcsec, sizeof(mcsec));

	mcsec.sh_name = w(old_shstr_sh_size);
	mcsec.sh_type = (sizeof(Elf_Rela) == rel_entsize)
		? w(SHT_RELA)
		: w(SHT_REL);
	mcsec.sh_flags = 0;
	mcsec.sh_addr = 0;
	mcsec.sh_offset = _w((void *)mlocp - (void *)mloc0 + t);
	mcsec.sh_size   = _w((void *)mrelp - (void *)mrel0);
	mcsec.sh_link = w(symsec_sh_link);
	mcsec.sh_info = w(old_shnum);
	mcsec.sh_addralign = _w(_size);
	mcsec.sh_entsize = _w(rel_entsize);
	uwrite(fd_map, &mcsec, sizeof(mcsec));

	uwrite(fd_map, mloc0, (void *)mlocp - (void *)mloc0);
	uwrite(fd_map, mrel0, (void *)mrelp - (void *)mrel0);

	ehdr->e_shoff = _w(new_e_shoff);
	ehdr->e_shnum = w2(2 + w2(ehdr->e_shnum));  /* {.rel,}__mcount_loc */
	ulseek(fd_map, 0, SEEK_SET);
	uwrite(fd_map, ehdr, sizeof(*ehdr));
}

/*
 * Look at the relocations in order to find the calls to mcount.
 * Accumulate the section offsets that are found, and their relocation info,
 * onto the end of the existing arrays.
 */
static uint_t *sift_rel_mcount(uint_t *mlocp,
			       unsigned const offbase,
			       Elf_Rel **const mrelpp,
			       Elf_Shdr const *const relhdr,
			       Elf_Ehdr const *const ehdr,
			       unsigned const recsym,
			       uint_t const recval,
			       unsigned const reltype)
{
	uint_t *const mloc0 = mlocp;
	Elf_Rel *mrelp = *mrelpp;
	Elf_Shdr *const shdr0 = (Elf_Shdr *)(_w(ehdr->e_shoff)
		+ (void *)ehdr);
	unsigned const symsec_sh_link = w(relhdr->sh_link);
	Elf_Shdr const *const symsec = &shdr0[symsec_sh_link];
	Elf_Sym const *const sym0 = (Elf_Sym const *)(_w(symsec->sh_offset)
		+ (void *)ehdr);

	Elf_Shdr const *const strsec = &shdr0[w(symsec->sh_link)];
	char const *const str0 = (char const *)(_w(strsec->sh_offset)
		+ (void *)ehdr);

	Elf_Rel const *const rel0 = (Elf_Rel const *)(_w(relhdr->sh_offset)
		+ (void *)ehdr);
	unsigned rel_entsize = _w(relhdr->sh_entsize);
	unsigned const nrel = _w(relhdr->sh_size) / rel_entsize;
	Elf_Rel const *relp = rel0;

	unsigned mcountsym = 0;
	unsigned t;

	for (t = nrel; t; --t) {
		if (!mcountsym) {
			Elf_Sym const *const symp =
				&sym0[Elf_r_sym(relp)];
			char const *symname = &str0[w(symp->st_name)];
			char const *mcount = gpfx == '_' ? "_mcount" : "mcount";

			if (symname[0] == '.')
				++symname;  /* ppc64 hack */
			if (strcmp(mcount, symname) == 0 ||
			    (altmcount && strcmp(altmcount, symname) == 0))
				mcountsym = Elf_r_sym(relp);
		}

		if (mcountsym == Elf_r_sym(relp) && !is_fake_mcount(relp)) {
			uint_t const addend = _w(_w(relp->r_offset) - recval);

			mrelp->r_offset = _w(offbase
				+ ((void *)mlocp - (void *)mloc0));
			Elf_r_info(mrelp, recsym, reltype);
			if (rel_entsize == sizeof(Elf_Rela)) {
				((Elf_Rela *)mrelp)->r_addend = addend;
				*mlocp++ = 0;
			} else
				*mlocp++ = addend;

			mrelp = (Elf_Rel *)(rel_entsize + (void *)mrelp);
		}
		relp = (Elf_Rel const *)(rel_entsize + (void *)relp);
	}
	*mrelpp = mrelp;
	return mlocp;
}


/*
 * Find a symbol in the given section, to be used as the base for relocating
 * the table of offsets of calls to mcount.  A local or global symbol suffices,
 * but avoid a Weak symbol because it may be overridden; the change in value
 * would invalidate the relocations of the offsets of the calls to mcount.
 * Often the found symbol will be the unnamed local symbol generated by
 * GNU 'as' for the start of each section.  For example:
 *    Num:    Value  Size Type    Bind   Vis      Ndx Name
 *      2: 00000000     0 SECTION LOCAL  DEFAULT    1
 */
static unsigned find_secsym_ndx(unsigned const txtndx,
				char const *const txtname,
				uint_t *const recvalp,
				Elf_Shdr const *const symhdr,
				Elf_Ehdr const *const ehdr)
{
	Elf_Sym const *const sym0 = (Elf_Sym const *)(_w(symhdr->sh_offset)
		+ (void *)ehdr);
	unsigned const nsym = _w(symhdr->sh_size) / _w(symhdr->sh_entsize);
	Elf_Sym const *symp;
	unsigned t;

	for (symp = sym0, t = nsym; t; --t, ++symp) {
		unsigned int const st_bind = ELF_ST_BIND(symp->st_info);

		if (txtndx == w2(symp->st_shndx)
			/* avoid STB_WEAK */
		    && (STB_LOCAL == st_bind || STB_GLOBAL == st_bind)) {
			*recvalp = _w(symp->st_value);
			return symp - sym0;
		}
	}
	fprintf(stderr, "Cannot find symbol for section %d: %s.\n",
		txtndx, txtname);
	fail_file();
}


/* Evade ISO C restriction: no declaration after statement in has_rel_mcount. */
static char const *
__has_rel_mcount(Elf_Shdr const *const relhdr,  /* is SHT_REL or SHT_RELA */
		 Elf_Shdr const *const shdr0,
		 char const *const shstrtab,
		 char const *const fname)
{
	/* .sh_info depends on .sh_type == SHT_REL[,A] */
	Elf_Shdr const *const txthdr = &shdr0[w(relhdr->sh_info)];
	char const *const txtname = &shstrtab[w(txthdr->sh_name)];

	if (strcmp("__mcount_loc", txtname) == 0) {
		fprintf(stderr, "warning: __mcount_loc already exists: %s\n",
			fname);
		succeed_file();
	}
	if (w(txthdr->sh_type) != SHT_PROGBITS ||
	    !(w(txthdr->sh_flags) & SHF_EXECINSTR) ||
	    !is_mcounted_section_name(txtname))
		return NULL;
	return txtname;
}

static char const *has_rel_mcount(Elf_Shdr const *const relhdr,
				  Elf_Shdr const *const shdr0,
				  char const *const shstrtab,
				  char const *const fname)
{
	if (w(relhdr->sh_type) != SHT_REL && w(relhdr->sh_type) != SHT_RELA)
		return NULL;
	return __has_rel_mcount(relhdr, shdr0, shstrtab, fname);
}


static unsigned tot_relsize(Elf_Shdr const *const shdr0,
			    unsigned nhdr,
			    const char *const shstrtab,
			    const char *const fname)
{
	unsigned totrelsz = 0;
	Elf_Shdr const *shdrp = shdr0;

	for (; nhdr; --nhdr, ++shdrp) {
		if (has_rel_mcount(shdrp, shdr0, shstrtab, fname))
			totrelsz += _w(shdrp->sh_size);
	}
	return totrelsz;
}


/* Overall supervision for Elf32 ET_REL file. */
static void
do_func(Elf_Ehdr *const ehdr, char const *const fname, unsigned const reltype)
{
	Elf_Shdr *const shdr0 = (Elf_Shdr *)(_w(ehdr->e_shoff)
		+ (void *)ehdr);
	unsigned const nhdr = w2(ehdr->e_shnum);
	Elf_Shdr *const shstr = &shdr0[w2(ehdr->e_shstrndx)];
	char const *const shstrtab = (char const *)(_w(shstr->sh_offset)
		+ (void *)ehdr);

	Elf_Shdr const *relhdr;
	unsigned k;

	/* Upper bound on space: assume all relevant relocs are for mcount. */
	unsigned const totrelsz = tot_relsize(shdr0, nhdr, shstrtab, fname);
	Elf_Rel *const mrel0 = umalloc(totrelsz);
	Elf_Rel *      mrelp = mrel0;

	/* 2*sizeof(address) <= sizeof(Elf_Rel) */
	uint_t *const mloc0 = umalloc(totrelsz>>1);
	uint_t *      mlocp = mloc0;

	unsigned rel_entsize = 0;
	unsigned symsec_sh_link = 0;

	for (relhdr = shdr0, k = nhdr; k; --k, ++relhdr) {
		char const *const txtname = has_rel_mcount(relhdr, shdr0,
			shstrtab, fname);
		if (txtname) {
			uint_t recval = 0;
			unsigned const recsym = find_secsym_ndx(
				w(relhdr->sh_info), txtname, &recval,
				&shdr0[symsec_sh_link = w(relhdr->sh_link)],
				ehdr);

			rel_entsize = _w(relhdr->sh_entsize);
			mlocp = sift_rel_mcount(mlocp,
				(void *)mlocp - (void *)mloc0, &mrelp,
				relhdr, ehdr, recsym, recval, reltype);
		}
	}
	if (mloc0 != mlocp) {
		append_func(ehdr, shstr, mloc0, mlocp, mrel0, mrelp,
			    rel_entsize, symsec_sh_link);
	}
	free(mrel0);
	free(mloc0);
}
Commit	Line	Data
c28d5077 SR	1	/*
	2	* recordmcount.h
	3	*
	4	* This code was taken out of recordmcount.c written by
	5	* Copyright 2009 John F. Reiser <jreiser@BitWagon.com>. All rights reserved.
	6	*
	7	* The original code had the same algorithms for both 32bit
	8	* and 64bit ELF files, but the code was duplicated to support
	9	* the difference in structures that were used. This
	10	* file creates a macro of everything that is different between
	11	* the 64 and 32 bit code, such that by including this header
	12	* twice we can create both sets of functions by including this
	13	* header once with RECORD_MCOUNT_64 undefined, and again with
	14	* it defined.
	15	*
	16	* This conversion to macros was done by:
	17	* Copyright 2010 Steven Rostedt <srostedt@redhat.com>, Red Hat Inc.
	18	*
	19	* Licensed under the GNU General Public License, version 2 (GPLv2).
	20	*/
	21	#undef append_func
412910cd WZ	22	#undef is_fake_mcount
	23	#undef fn_is_fake_mcount
	24	#undef MIPS_is_fake_mcount
c28d5077 SR	25	#undef sift_rel_mcount
	26	#undef find_secsym_ndx
	27	#undef __has_rel_mcount
	28	#undef has_rel_mcount
	29	#undef tot_relsize
	30	#undef do_func
412910cd	31	#undef Elf_Addr
c28d5077 SR	32	#undef Elf_Ehdr
	33	#undef Elf_Shdr
	34	#undef Elf_Rel
	35	#undef Elf_Rela
	36	#undef Elf_Sym
	37	#undef ELF_R_SYM
a2d49358	38	#undef Elf_r_sym
c28d5077	39	#undef ELF_R_INFO
a2d49358	40	#undef Elf_r_info
c28d5077	41	#undef ELF_ST_BIND
a2d49358 JR	42	#undef fn_ELF_R_SYM
a2d49358 JR	43	#undef fn_ELF_R_INFO
c28d5077 SR	44	#undef uint_t
	45	#undef _w
	46	#undef _align
	47	#undef _size
	48
	49	#ifdef RECORD_MCOUNT_64
	50	# define append_func append64
	51	# define sift_rel_mcount sift64_rel_mcount
	52	# define find_secsym_ndx find64_secsym_ndx
	53	# define __has_rel_mcount __has64_rel_mcount
	54	# define has_rel_mcount has64_rel_mcount
	55	# define tot_relsize tot64_relsize
	56	# define do_func do64
412910cd WZ	57	# define is_fake_mcount is_fake_mcount64
	58	# define fn_is_fake_mcount fn_is_fake_mcount64
	59	# define MIPS_is_fake_mcount MIPS64_is_fake_mcount
	60	# define Elf_Addr Elf64_Addr
c28d5077 SR	61	# define Elf_Ehdr Elf64_Ehdr
	62	# define Elf_Shdr Elf64_Shdr
	63	# define Elf_Rel Elf64_Rel
	64	# define Elf_Rela Elf64_Rela
	65	# define Elf_Sym Elf64_Sym
	66	# define ELF_R_SYM ELF64_R_SYM
a2d49358	67	# define Elf_r_sym Elf64_r_sym
c28d5077	68	# define ELF_R_INFO ELF64_R_INFO
a2d49358	69	# define Elf_r_info Elf64_r_info
c28d5077	70	# define ELF_ST_BIND ELF64_ST_BIND
a2d49358 JR	71	# define fn_ELF_R_SYM fn_ELF64_R_SYM
a2d49358 JR	72	# define fn_ELF_R_INFO fn_ELF64_R_INFO
c28d5077 SR	73	# define uint_t uint64_t
	74	# define _w w8
	75	# define _align 7u
	76	# define _size 8
	77	#else
	78	# define append_func append32
	79	# define sift_rel_mcount sift32_rel_mcount
	80	# define find_secsym_ndx find32_secsym_ndx
	81	# define __has_rel_mcount __has32_rel_mcount
	82	# define has_rel_mcount has32_rel_mcount
	83	# define tot_relsize tot32_relsize
	84	# define do_func do32
412910cd WZ	85	# define is_fake_mcount is_fake_mcount32
	86	# define fn_is_fake_mcount fn_is_fake_mcount32
	87	# define MIPS_is_fake_mcount MIPS32_is_fake_mcount
	88	# define Elf_Addr Elf32_Addr
c28d5077 SR	89	# define Elf_Ehdr Elf32_Ehdr
	90	# define Elf_Shdr Elf32_Shdr
	91	# define Elf_Rel Elf32_Rel
	92	# define Elf_Rela Elf32_Rela
	93	# define Elf_Sym Elf32_Sym
	94	# define ELF_R_SYM ELF32_R_SYM
a2d49358	95	# define Elf_r_sym Elf32_r_sym
c28d5077	96	# define ELF_R_INFO ELF32_R_INFO
a2d49358	97	# define Elf_r_info Elf32_r_info
c28d5077	98	# define ELF_ST_BIND ELF32_ST_BIND
a2d49358 JR	99	# define fn_ELF_R_SYM fn_ELF32_R_SYM
a2d49358 JR	100	# define fn_ELF_R_INFO fn_ELF32_R_INFO
c28d5077 SR	101	# define uint_t uint32_t
	102	# define _w w
	103	# define _align 3u
	104	# define _size 4
	105	#endif
	106
412910cd WZ	107	/* Functions and pointers that do_file() may override for specific e_machine. */
	108	static int fn_is_fake_mcount(Elf_Rel const *rp)
	109	{
	110	return 0;
	111	}
	112	static int (is_fake_mcount)(Elf_Rel const rp) = fn_is_fake_mcount;
	113
a2d49358 JR	114	static uint_t fn_ELF_R_SYM(Elf_Rel const *rp)
	115	{
	116	return ELF_R_SYM(_w(rp->r_info));
	117	}
	118	static uint_t (Elf_r_sym)(Elf_Rel const rp) = fn_ELF_R_SYM;
	119
	120	static void fn_ELF_R_INFO(Elf_Rel *const rp, unsigned sym, unsigned type)
	121	{
e63233f7	122	rp->r_info = _w(ELF_R_INFO(sym, type));
a2d49358 JR	123	}
	124	static void (Elf_r_info)(Elf_Rel const rp, unsigned sym, unsigned type) = fn_ELF_R_INFO;
	125
412910cd WZ	126	/*
	127	* MIPS mcount long call has 2 _mcount symbols, only the position of the 1st
	128	* _mcount symbol is needed for dynamic function tracer, with it, to disable
	129	* tracing(ftrace_make_nop), the instruction in the position is replaced with
	130	* the "b label" instruction, to enable tracing(ftrace_make_call), replace the
	131	* instruction back. So, here, we set the 2nd one as fake and filter it.
	132	*
	133	* c: 3c030000 lui v1,0x0 <--> b label
	134	* c: R_MIPS_HI16 _mcount
	135	* c: R_MIPS_NONE ABS
	136	* c: R_MIPS_NONE ABS
	137	* 10: 64630000 daddiu v1,v1,0
	138	* 10: R_MIPS_LO16 _mcount
	139	* 10: R_MIPS_NONE ABS
	140	* 10: R_MIPS_NONE ABS
	141	* 14: 03e0082d move at,ra
	142	* 18: 0060f809 jalr v1
	143	* label:
	144	*/
	145	#define MIPS_FAKEMCOUNT_OFFSET 4
	146
	147	static int MIPS_is_fake_mcount(Elf_Rel const *rp)
	148	{
	149	static Elf_Addr old_r_offset;
	150	Elf_Addr current_r_offset = _w(rp->r_offset);
	151	int is_fake;
	152
	153	is_fake = old_r_offset &&
	154	(current_r_offset - old_r_offset == MIPS_FAKEMCOUNT_OFFSET);
	155	old_r_offset = current_r_offset;
	156
	157	return is_fake;
	158	}
a2d49358	159
c28d5077 SR	160	/* Append the new shstrtab, Elf_Shdr[], __mcount_loc and its relocations. */
	161	static void append_func(Elf_Ehdr *const ehdr,
	162	Elf_Shdr *const shstr,
	163	uint_t const *const mloc0,
	164	uint_t const *const mlocp,
	165	Elf_Rel const *const mrel0,
	166	Elf_Rel const *const mrelp,
	167	unsigned int const rel_entsize,
	168	unsigned int const symsec_sh_link)
	169	{
	170	/* Begin constructing output file */
	171	Elf_Shdr mcsec;
	172	char const *mc_name = (sizeof(Elf_Rela) == rel_entsize)
	173	? ".rela__mcount_loc"
	174	: ".rel__mcount_loc";
	175	unsigned const old_shnum = w2(ehdr->e_shnum);
	176	uint_t const old_shoff = _w(ehdr->e_shoff);
	177	uint_t const old_shstr_sh_size = _w(shstr->sh_size);
	178	uint_t const old_shstr_sh_offset = _w(shstr->sh_offset);
	179	uint_t t = 1 + strlen(mc_name) + _w(shstr->sh_size);
	180	uint_t new_e_shoff;
	181
	182	shstr->sh_size = _w(t);
	183	shstr->sh_offset = _w(sb.st_size);
	184	t += sb.st_size;
	185	t += (_align & -t); /* word-byte align */
	186	new_e_shoff = t;
	187
	188	/* body for new shstrtab */
	189	ulseek(fd_map, sb.st_size, SEEK_SET);
	190	uwrite(fd_map, old_shstr_sh_offset + (void *)ehdr, old_shstr_sh_size);
	191	uwrite(fd_map, mc_name, 1 + strlen(mc_name));
	192
	193	/* old(modified) Elf_Shdr table, word-byte aligned */
	194	ulseek(fd_map, t, SEEK_SET);
	195	t += sizeof(Elf_Shdr) * old_shnum;
	196	uwrite(fd_map, old_shoff + (void *)ehdr,
	197	sizeof(Elf_Shdr) * old_shnum);
	198
	199	/* new sections __mcount_loc and .rel__mcount_loc */
	200	t += 2*sizeof(mcsec);
	201	mcsec.sh_name = w((sizeof(Elf_Rela) == rel_entsize) + strlen(".rel")
	202	+ old_shstr_sh_size);
	203	mcsec.sh_type = w(SHT_PROGBITS);
	204	mcsec.sh_flags = _w(SHF_ALLOC);
	205	mcsec.sh_addr = 0;
	206	mcsec.sh_offset = _w(t);
	207	mcsec.sh_size = _w((void )mlocp - (void )mloc0);
	208	mcsec.sh_link = 0;
	209	mcsec.sh_info = 0;
	210	mcsec.sh_addralign = _w(_size);
	211	mcsec.sh_entsize = _w(_size);
	212	uwrite(fd_map, &mcsec, sizeof(mcsec));
	213
	214	mcsec.sh_name = w(old_shstr_sh_size);
	215	mcsec.sh_type = (sizeof(Elf_Rela) == rel_entsize)
	216	? w(SHT_RELA)
	217	: w(SHT_REL);
	218	mcsec.sh_flags = 0;
	219	mcsec.sh_addr = 0;
	220	mcsec.sh_offset = _w((void )mlocp - (void )mloc0 + t);
	221	mcsec.sh_size = _w((void )mrelp - (void )mrel0);
	222	mcsec.sh_link = w(symsec_sh_link);
	223	mcsec.sh_info = w(old_shnum);
224	mcsec.sh_addralign = _w(_size);
225	mcsec.sh_entsize = _w(rel_entsize);
226	uwrite(fd_map, &mcsec, sizeof(mcsec));
227
228	uwrite(fd_map, mloc0, (void )mlocp - (void )mloc0);
229	uwrite(fd_map, mrel0, (void )mrelp - (void )mrel0);
230
231	ehdr->e_shoff = _w(new_e_shoff);
232	ehdr->e_shnum = w2(2 + w2(ehdr->e_shnum)); /* {.rel,}__mcount_loc */
233	ulseek(fd_map, 0, SEEK_SET);
234	uwrite(fd_map, ehdr, sizeof(*ehdr));
235	}
236
c28d5077 SR	237	/*
	238	* Look at the relocations in order to find the calls to mcount.
	239	* Accumulate the section offsets that are found, and their relocation info,
	240	* onto the end of the existing arrays.
	241	*/
	242	static uint_t sift_rel_mcount(uint_t mlocp,
	243	unsigned const offbase,
	244	Elf_Rel **const mrelpp,
	245	Elf_Shdr const *const relhdr,
	246	Elf_Ehdr const *const ehdr,
	247	unsigned const recsym,
	248	uint_t const recval,
	249	unsigned const reltype)
	250	{
	251	uint_t *const mloc0 = mlocp;
	252	Elf_Rel mrelp = mrelpp;
	253	Elf_Shdr const shdr0 = (Elf_Shdr )(_w(ehdr->e_shoff)
	254	+ (void *)ehdr);
	255	unsigned const symsec_sh_link = w(relhdr->sh_link);
	256	Elf_Shdr const *const symsec = &shdr0[symsec_sh_link];
	257	Elf_Sym const const sym0 = (Elf_Sym const )(_w(symsec->sh_offset)
	258	+ (void *)ehdr);
	259
	260	Elf_Shdr const *const strsec = &shdr0[w(symsec->sh_link)];
	261	char const const str0 = (char const )(_w(strsec->sh_offset)
	262	+ (void *)ehdr);
	263
	264	Elf_Rel const const rel0 = (Elf_Rel const )(_w(relhdr->sh_offset)
	265	+ (void *)ehdr);
	266	unsigned rel_entsize = _w(relhdr->sh_entsize);
	267	unsigned const nrel = _w(relhdr->sh_size) / rel_entsize;
	268	Elf_Rel const *relp = rel0;
	269
	270	unsigned mcountsym = 0;
	271	unsigned t;
	272
	273	for (t = nrel; t; --t) {
	274	if (!mcountsym) {
	275	Elf_Sym const *const symp =
a2d49358	276	&sym0[Elf_r_sym(relp)];
c28d5077	277	char const *symname = &str0[w(symp->st_name)];
dd5477ff	278	char const *mcount = gpfx == '_' ? "_mcount" : "mcount";
c28d5077	279
dd5477ff	280	if (symname[0] == '.')
c28d5077	281	++symname; /* ppc64 hack */
dd5477ff SR	282	if (strcmp(mcount, symname) == 0 \|\|
dd5477ff SR	283	(altmcount && strcmp(altmcount, symname) == 0))
a2d49358	284	mcountsym = Elf_r_sym(relp);
c28d5077 SR	285	}
c28d5077 SR	286
412910cd	287	if (mcountsym == Elf_r_sym(relp) && !is_fake_mcount(relp)) {
c28d5077 SR	288	uint_t const addend = _w(_w(relp->r_offset) - recval);
	289
	290	mrelp->r_offset = _w(offbase
	291	+ ((void )mlocp - (void )mloc0));
a2d49358	292	Elf_r_info(mrelp, recsym, reltype);
dd5477ff	293	if (rel_entsize == sizeof(Elf_Rela)) {
c28d5077 SR	294	((Elf_Rela *)mrelp)->r_addend = addend;
	295	*mlocp++ = 0;
	296	} else
	297	*mlocp++ = addend;
	298
	299	mrelp = (Elf_Rel )(rel_entsize + (void )mrelp);
	300	}
	301	relp = (Elf_Rel const )(rel_entsize + (void )relp);
	302	}
	303	*mrelpp = mrelp;
	304	return mlocp;
	305	}
	306
	307
	308	/*
	309	* Find a symbol in the given section, to be used as the base for relocating
	310	* the table of offsets of calls to mcount. A local or global symbol suffices,
	311	* but avoid a Weak symbol because it may be overridden; the change in value
	312	* would invalidate the relocations of the offsets of the calls to mcount.
	313	* Often the found symbol will be the unnamed local symbol generated by
	314	* GNU 'as' for the start of each section. For example:
	315	* Num: Value Size Type Bind Vis Ndx Name
	316	* 2: 00000000 0 SECTION LOCAL DEFAULT 1
	317	*/
	318	static unsigned find_secsym_ndx(unsigned const txtndx,
	319	char const *const txtname,
	320	uint_t *const recvalp,
	321	Elf_Shdr const *const symhdr,
	322	Elf_Ehdr const *const ehdr)
	323	{
	324	Elf_Sym const const sym0 = (Elf_Sym const )(_w(symhdr->sh_offset)
	325	+ (void *)ehdr);
	326	unsigned const nsym = _w(symhdr->sh_size) / _w(symhdr->sh_entsize);
	327	Elf_Sym const *symp;
	328	unsigned t;
	329
	330	for (symp = sym0, t = nsym; t; --t, ++symp) {
	331	unsigned int const st_bind = ELF_ST_BIND(symp->st_info);
	332
	333	if (txtndx == w2(symp->st_shndx)
	334	/* avoid STB_WEAK */
	335	&& (STB_LOCAL == st_bind \|\| STB_GLOBAL == st_bind)) {
	336	*recvalp = _w(symp->st_value);
	337	return symp - sym0;
	338	}
	339	}
	340	fprintf(stderr, "Cannot find symbol for section %d: %s.\n",
	341	txtndx, txtname);
	342	fail_file();
	343	}
	344
	345
	346	/* Evade ISO C restriction: no declaration after statement in has_rel_mcount. */
	347	static char const *
	348	__has_rel_mcount(Elf_Shdr const const relhdr, / is SHT_REL or SHT_RELA */
	349	Elf_Shdr const *const shdr0,
	350	char const *const shstrtab,
	351	char const *const fname)
	352	{
	353	/* .sh_info depends on .sh_type == SHT_REL[,A] */
	354	Elf_Shdr const *const txthdr = &shdr0[w(relhdr->sh_info)];
	355	char const *const txtname = &shstrtab[w(txthdr->sh_name)];
	356
dd5477ff	357	if (strcmp("__mcount_loc", txtname) == 0) {
c28d5077 SR	358	fprintf(stderr, "warning: __mcount_loc already exists: %s\n",
	359	fname);
	360	succeed_file();
	361	}
dd5477ff	362	if (w(txthdr->sh_type) != SHT_PROGBITS \|\|
8abd5724	363	!(w(txthdr->sh_flags) & SHF_EXECINSTR) \|\|
c28d5077 SR	364	!is_mcounted_section_name(txtname))
	365	return NULL;
	366	return txtname;
	367	}
	368
	369	static char const has_rel_mcount(Elf_Shdr const const relhdr,
	370	Elf_Shdr const *const shdr0,
	371	char const *const shstrtab,
	372	char const *const fname)
	373	{
dd5477ff	374	if (w(relhdr->sh_type) != SHT_REL && w(relhdr->sh_type) != SHT_RELA)
c28d5077 SR	375	return NULL;
	376	return __has_rel_mcount(relhdr, shdr0, shstrtab, fname);
	377	}
	378
	379
	380	static unsigned tot_relsize(Elf_Shdr const *const shdr0,
	381	unsigned nhdr,
	382	const char *const shstrtab,
	383	const char *const fname)
	384	{
	385	unsigned totrelsz = 0;
	386	Elf_Shdr const *shdrp = shdr0;
	387
	388	for (; nhdr; --nhdr, ++shdrp) {
	389	if (has_rel_mcount(shdrp, shdr0, shstrtab, fname))
	390	totrelsz += _w(shdrp->sh_size);
	391	}
	392	return totrelsz;
	393	}
	394
	395
	396	/* Overall supervision for Elf32 ET_REL file. */
	397	static void
	398	do_func(Elf_Ehdr const ehdr, char const const fname, unsigned const reltype)
	399	{
	400	Elf_Shdr const shdr0 = (Elf_Shdr )(_w(ehdr->e_shoff)
	401	+ (void *)ehdr);
	402	unsigned const nhdr = w2(ehdr->e_shnum);
	403	Elf_Shdr *const shstr = &shdr0[w2(ehdr->e_shstrndx)];
	404	char const const shstrtab = (char const )(_w(shstr->sh_offset)
	405	+ (void *)ehdr);
	406
	407	Elf_Shdr const *relhdr;
	408	unsigned k;
	409
	410	/* Upper bound on space: assume all relevant relocs are for mcount. */
	411	unsigned const totrelsz = tot_relsize(shdr0, nhdr, shstrtab, fname);
	412	Elf_Rel *const mrel0 = umalloc(totrelsz);
	413	Elf_Rel * mrelp = mrel0;
	414
	415	/* 2sizeof(address) <= sizeof(Elf_Rel) /
	416	uint_t *const mloc0 = umalloc(totrelsz>>1);
	417	uint_t * mlocp = mloc0;
	418
	419	unsigned rel_entsize = 0;
	420	unsigned symsec_sh_link = 0;
	421
	422	for (relhdr = shdr0, k = nhdr; k; --k, ++relhdr) {
	423	char const *const txtname = has_rel_mcount(relhdr, shdr0,
	424	shstrtab, fname);
	425	if (txtname) {
	426	uint_t recval = 0;
	427	unsigned const recsym = find_secsym_ndx(
	428	w(relhdr->sh_info), txtname, &recval,
	429	&shdr0[symsec_sh_link = w(relhdr->sh_link)],
	430	ehdr);
	431
	432	rel_entsize = _w(relhdr->sh_entsize);
	433	mlocp = sift_rel_mcount(mlocp,
	434	(void )mlocp - (void )mloc0, &mrelp,
	435	relhdr, ehdr, recsym, recval, reltype);
	436	}
	437	}
	438	if (mloc0 != mlocp) {
439	append_func(ehdr, shstr, mloc0, mlocp, mrel0, mrelp,
440	rel_entsize, symsec_sh_link);
441	}
442	free(mrel0);
443	free(mloc0);
444	}